Identification of differentially expressed genes in human lung squamous cell carcinoma in Asian Indians using suppression subtractive hybridization

A71 Background: Lung cancer (LC) is notorious for early metastasis and very high mortality, worldwide. Asian Indian lung cancer patients differ from their Western counterparts as they present almost 15-20 years earlier, squamous cell carcinoma (SCC) being the commonest histological type. Lung squamous cell carcinoma (LSCC) and matched normal lung tissues were compared for the first time in Asian Indians to identify and characterize differentially expressed genes involved in lung carcinogenesis. Methods: Two subtracted cDNA libraries containing up- and down-regulated genes in the tumors were constructed using suppression subtractive hybridization (SSH). The differential expression of these genes was confirmed by reverse Northern blot analysis. DNA of confirmed clones was sequenced and subjected to GenBank Blast searches. RNA expression levels were then individually analyzed by semiquantitative RT-PCR and Northern blotting. Results: By this technique, 17 differentially expressed gene cDNA fragments of LSCC were obtained. The differentially expressed genes included those associated with cell cycle, cell structure, cell adhesion, cellular metabolism, apoptosis, transcription, proliferation and signal transduction. RT-PCR analysis and Northern blotting of lung tumor and matched normal lung tissues provided the first evidence that KIAA0767, a mitochondrial death inducing protein, a novel p53 independent target of E2F1 and Geminin, an inhibitor of DNA replication are differentially expressed in LSCC. Conclusions: Identification of the differentially expressed genes in lung cancer in this study adds to the repertoire of genes associated with lung tumorigenesis and may serve as better molecular markers that can benefit the patient with respect to early diagnosis, determining response to chemo/radiotherapy and identifying novel putative intervention sites for anticancer therapy. This is the first such study in Asian Indians. Further characterization of differentially expressed cDNAs identified in this study may help in better understanding of lung carcinogenesis at the molecular/genetic level.